Robert a



' UNITED sTA'rEsrATnNT. oFFroE.

nonnn'r n nanrmnnror WESTMINSTER, ma

mnrnon or 'rouen'mime rnozrncrmns.

land, have invented new and useful Impiercing projectiles, it

.provements in Methods of Toughening Projectiles, ofwhich the following is a specification, a

' My invention relates to armor piercing projectiles and the projectiles are greatly improved as'to the toughness of the hardened portions and also asto uniformity both in toughness and hardness. Y Y

In'the manufacturing of hardened armor has been found that after these have been duly heated, treated and hardened, there is often. considerable variation in the hardness at various points and in the character'of the hardness. In case of overhardening either in spots orof the whole point, oreven when not overhardened, the hardened ortion is not so tough as it should be. onsequently when such a projectile, cap, strikes an armor plate, it isliable to crack and such cracking, may break up the whole projectile and prevent penetrat on.

1 hav discovered that if the projectile is then reheated to a substantial degree that is to from 100 C. to 200 C. or: even-to some diminution in' the hardness,

250 C. there is a-substa'ntial increase in the toughness. This increase is to some extent inproportion to the degree of heatingand the temperatures the tougher will the'higher be the product, but as it is-accompanied by the heatingshould not becarried toofar'that-is not above about 250 C. at the highest.

1 Asanexample of the treatment;' au armor piercing projectile 0f-12- cm. caliber was "hardened in the usual manner and the forward portion of the projectile heated to about 250 base, it being understood that the projectile was about 12-" in length. Ttwas then plunged in the oil bath to'its base and maindo drawn and permitted tainedv consists in a method whereby v to about 150 (3., whereby the toughness w either with or without a C. to. within aboutB" of the there for a short time, then withto cool in the air. It

Specification of Letters Patent. I t nt 23,191 No Drawing. Application filed April 22, 1914, Serial No. 833,620. Renewed September 18, 1919. Serial No.-

'. was found that the toughness of this pro creased, in. fact to such an extent in some cases asto permit an 8 bend. This i an extraordinary result for hardened steel, for. it will be understood that ordinary hardened steel under the shot test gives practically no bending "angle at all.

As aforesaid the tempering temperature may be greatly varied and may be carried to as high as 250 C. or. thereabout, but in some cases it will 'be desirable to heat on 1 be decidedly increased Without danger of substantially reducing the hardness.

I claim, 1. The method of toughening hardened armor piercing projectiles which consists, after hardening, to about 150 C., then rmitting it to cool.

2. The herein descri d process of increasing the toughness of hardened projectiles and the like which consists in heating the article from over 100 C. to not over 250 C. and then permitting the article to cool.

- 3. The herein. described method of increasing the toughness and making uniform the. hardness of hardened armor piercing projectiles of a substantial size for instance not less than about twelve by three inches, which consists in heating the projectile to a 6., then plunging the projectilein an oil Y bath, thentaking it out and. permitting it signed my OBERT A.

Witnesses:

A. F. SASSEEN, J. R. MRLWARD.

in heating the projectile egmparatively low degree and above about 

